That global warming would endanger coral reefs, scientists have known for a long time. But new work today shows a reality that they had not dared to imagine. Because, with temperatures 1.5°C higher than those of the pre-industrial era, corals will have a hard time finding viable refuges for them on our Earth.
One Coral reef, it is much more than a simple assembly of corals. It’s a ecosystem complex sailor. One of the richest ecosystems in biodiversity. In authorized circles, it is rumored that coral reefs offer food, refuge and even protection to no less than a quarter of marine life. More than 4,000 species of Pisces. And they constitute in fact, one can easily imagine, a non-negligible source of income and food for many people. Half a billion, according to estimates.
Unfortunately, corals thrive in a fairly specific temperature range. This makes them particularly vulnerable to variations in the weather. So, with the global warming anthropogenic and not only the rise in ocean temperature, but also the multiplication and intensification of waves of heat marine life, coral reefs are in danger. More and more episodes of bleaching — a discoloration that weakens the coral and from which it takes about ten years to recover – and even the death of corals are reported.
In 2018, the Intergovernmental Panel on Climate Change (IPCC) alerted. If our Earth were to warm by just 1.5°C above pre-industrial averages — a best-case scenario of the Paris Climate Agreement commitments — between 70 and 90 percent of coral reefs could disappear. Today, some University of Leeds researchers (UK) make a conclusion even more stark. At 1.5°C of warming, 99% of corals will face too frequent heat waves for them to recover. However, +1.5°C is where we will be at the start of the 2030s if drastic measures to reduce our emissions of greenhouse gas are not taken immediately.
A single solution: limit our greenhouse gas emissions
Using historical data, satellite images and climate projections, the researchers show more accurately that, whereas over the past few decades, 84% of tropical corals may have had enough time between two heat waves to recover from bleaching episodes, in a warmer world of 1 .5°C, they will only be… 0.2%! And scientists have managed to identify the only thermal refuges that could remain. On the side of Polynesia and the Coral Triangle – a small region of the Pacific in which Malaysia, Indonesia, the Philippines and the Solomon Islands are located. Thanks to a lower rate of warming and episodes of colder waters rising to the surface.
Thus, the researchers call for the implementation of operations to protect these refuges. Actions aimed at eliminating other risk factors stress such as fishing, tourism, water pollution. Or actions that promote the resistance, recovery or migration of corals. But the scientists point out that these operations can only be considered in the short term because, with a warming of 2°C, they already predict that none of the coral refuges will be able to remain.
This confirms once again that it is urgent to limit our emissions of greenhouse gas. That it is not only a question of meeting the commitments of the Paris Agreement on the climate, but of succeeding in exceeding them. For corals too, it’s a matter of life… or death!
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